Air Quality Modeling

The following models are available to assist the CEQA practitioner in calculating impact to air quality.

The following links will take you directly to these models: 

  • California Emission Estimator Model (CalEEMod)Link to external website.
    CalEEMod is a statewide land use emissions computer model designed to provide a uniform platform for government agencies, land use planners, and environmental professionals to quantify potential criteria pollutant and greenhouse gas (GHG) emissions associated with both construction and operational from a variety of land use projects.

  • California Air Resources Board (CARB) Models

Mobile Emissions ModelsLink to external website.
CARB has developed various mobile emissions models to assist CEQA practitioners for air quality impact assessment from on-road and offroad sources. Specifically, the EMFAC emissions model was developed and used by CARB to assess emissions from on-road vehicles including cars, trucks, and buses in California, and to support CARB's regulatory and air quality planning efforts to meet the Federal Highway Administration's transportation planning requirements. For offroad equipment, CARB developed the Off-Road model which is currently being replaced by category specific methods and inventory models that are being developed for specific regulatory support projects.

Hotspots Analysis and Reporting Program (HARP)Link to external website.
HARP is a software suite that was developed by California Air Resource Board (CARB) to assist with implementing the programmatic requirements of the Air Toxics "Hot Spots" Program.  HARP includes the following modules: emission inventory database, facility prioritization calculation, air dispersion modeling, and risk assessment analysis.  HARP can also be utilized for: 1) preparing risk assessments for other air-related activities as part of preparing CEQA documents; 2) evaluating air permit applications; 3) developing air toxic control measures; 4) conducting ambient monitoring evaluations; and 5) evaluating roadways.

  • United States Environmental Protection Agency (EPA) Models
    U.S. EPA has developed several air quality models and mathematical simulation techniques that can used in assessing control strategies and source impacts which are available on the Support Center for Regulatory Atmospheric Modeling (SCRAM) webpage, which include but are not limited to:

AERMOD Modeling System – One of U.S. EPA’s preferred and recommended air quality dispersion models. A steady-state plume model that incorporates air dispersion based on planetary boundary layer turbulence structure and scaling concepts, including treatment of both surface and elevated sources, and both simple and complex terrain.

Comprehensive Air Quality Model with extensions (CAMx)
– One of U.S. EPA’s photochemical air quality models, the CAMx model simulates air quality over many geographic scales. The model treats a wide variety of inert and chemically active pollutants, including ozone, particulate matter, inorganic and organic PM2.5/PM10, and mercury and other toxics. CAMx also has plume-in-grid and source apportionment capabilities.

Community Multiscale Air Quality (CMAQ) 
– One of U.S. EPA’s photochemical air quality models, the CMAQ modeling system includes state-of-the-science capabilities for conducting urban-to-regional-to-hemispheric scale simulations of multiple air quality issues, including tropospheric ozone, fine particles, toxics, acid deposition, and visibility degradation.

U.S. EPA has also developed the RMP*Comp™ model for conducting an off-site consequence analyses (both worst case scenarios and alternative scenarios) required for compliance with U.S. EPA’s Risk Management Program rule. This model can also be relied upon to evaluate hazards and hazardous materials impacts under CEQA.

More Information

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